JP5475604B2 - Method for determining contact of shooting object - Google Patents

Description

  The present invention relates to a method for determining whether an object photographed by a camera is not in contact with a protective plate on the front surface of the camera.

In recent years, authentication devices using finger veins have become widespread. This device irradiates a finger with near-infrared rays, images the transmitted light or reflected light, extracts a vein portion from the image data, and performs pattern matching to determine whether or not the person is the person.
In order to protect the camera that shoots the finger that irradiates the finger with near infrared rays and to reduce the influence of visible light, a plate-like component that also has a property transparent to infrared rays between the finger and the camera (Hereinafter referred to as a filter) is often attached.
However, when a finger comes into contact with the filter, the vein is compressed and the vein portion becomes difficult to be seen, which affects the authentication performance. In particular, when the usage method of the finger vein authentication device is not well known, the user may mistakenly recognize it as a fingerprint authentication device, and may intentionally press the finger against the filter surface, resulting in a further deterioration in authentication performance. It was.
In addition, there exist the following as prior art literature regarding this invention.

JP 2006-155575 A

  Therefore, for example, a method of attaching a transparent electrode to the filter surface and determining whether the finger is in contact with the filter surface due to the change in capacitance can be considered. This is not a good idea.

  The objective of this invention is providing the contact determination apparatus of the imaging | photography object which can detect whether the finger | toe is contacting the filter surface at low cost.

The contact detection apparatus for an object to be photographed according to the present invention has a filter member on the lower surface portion, and has a finger rest that places the base part of the finger to be photographed from the base part to the tip part, and is placed on this finger rest. A near-infrared illumination device that irradiates near-infrared rays from the palm side of the finger to be imaged through the filter member, a camera that captures an image of the finger from the palm side through the filter member, and a finger that is captured by the camera A contact determination unit that determines whether the finger is in contact with the filter surface by processing the image of
The near-infrared illumination device that the near-infrared illumination device irradiates the finger to be imaged with respect to the imaging range of the camera is set to be narrow, and the contact determination unit determines the size of the shadow formed on the tip of the finger. It is characterized in that it is determined whether or not the finger is in contact with the filter surface.

  According to the present invention, since it is possible to determine whether or not a finger is in contact with the filter surface simply by processing a captured image, it is not necessary to mount an electrical component such as a transparent electrode, and it can be configured at low cost. .

It is a block block diagram which shows one Embodiment of the apparatus structure of this invention. It is a figure which shows the state in which the finger | toe is not contacting the filter member in the contact determination apparatus of the imaging | photography target object of this invention. In the imaging | photography target object contact determination apparatus of this invention, it is a figure which shows the image image | photographed in the state in which the finger is not contacting the filter member. In the imaging | photography target object contact determination apparatus of this invention, it is a figure which shows the state in which the finger is contacting the filter member. In the imaging | photography target object contact determination apparatus of this invention, it is a figure which shows the image image | photographed in the state which the finger is contacting. It is a figure explaining the part which determines the presence of a shadow in order to perform a contact determination. It is a flowchart which shows the determination process of a to-be-photographed object contact determination apparatus. It is a figure which shows other embodiment of this invention.

Hereinafter, an embodiment of a contact determination device for a photographing object to which the present invention is applied will be described.
FIG. 1 is a system configuration diagram of a photographing object contact determination device according to the present invention, and an infrared illumination device 102 irradiates a finger to be photographed with infrared rays with an output specified by a control unit 101, and in that state. The camera device 103 that has received an instruction from the control unit captures a finger and outputs image data, and the contact determination unit 104 that has received the instruction from the control unit 103 performs image processing to determine whether or not the finger is in contact. Is determined.

FIG. 2 shows a state where the photographing object is not in contact with the filter member when the photographing object contact determination device according to the present invention is used.
A finger 201 that is an object to be photographed is placed on the finger rests 202 and 208 having a transparent filter member 205 on the lower surface with the palm side facing down. An arrow 206 indicates the shooting range of the camera 204, and an arrow 207 indicates the irradiation range of the near infrared ray output from the near infrared LED 203. Further, the filter member 205 is disposed between the camera 204 and the finger 201 that is the object to be photographed, and the camera 204 captures an image of the finger 201 placed on the finger rests 202 and 208 via the filter member 205. It has become.
The near-infrared ray emitted from the near-infrared LED 203 is blocked at the L-shaped bottom portion of the finger rest 208 at the tip portion of the finger, so that a shadow 209 is formed on the tip portion (left side portion in the figure) of the finger 201. . Near-infrared LED 203 emits near-infrared LED 203 on the right side (base portion) of shadow 209 of finger 201 that is the object to be imaged.
The state of the image taken by the camera 204 in this state is as shown in FIG. That is, the portion irradiated with near infrared rays appears bright as indicated by reference numeral 302, and the portion corresponding to the shadow 209 in FIG.

  That is, the near-infrared LED 203 irradiates the finger 201 to be photographed with respect to the photographing range of the camera 204 so that the near-infrared irradiation range is set narrow, and the tip of the finger 201 is normal when the finger is not in contact with the filter member 205. A shadow 303 having a predetermined size is formed on the portion.

FIG. 4 is a diagram illustrating a state where the finger 201 is in contact with the filter member 205.
The finger 201 rides on the finger placing table 202, and the tip portion contacts the finger placing table 208 and further contacts the upper surface of the filter member 205.
Reference numeral 206 denotes a photographing range of the camera 204, and an arrow 207 denotes an irradiation range of the near infrared LED 203. In this case, the near-infrared light emitted from the near-infrared LED 203 creates a shadow 209 by the finger rest 208, but since this shadow 209 can be in the blind spot direction (outside the shooting range) of the camera 204, it is hardly reflected in the camera 204. .

The state of the image shot in this state is as shown in FIG. That is, a portion irradiated with near infrared rays appears bright as indicated by 502, and a portion corresponding to the shadow 209 in FIG.
As described above, the manner (size) of the shadow of the tip of the finger is different depending on whether the object to be photographed is in contact with the filter member 205 or not. Whether or not they are in contact can be determined by image processing.

The method for determining the presence or absence of a shadow from a captured image determines the presence or absence of a shadow by obtaining the average luminance of the pixels included in the rectangle 601 in FIG. 6 and comparing it with a specific threshold value. The position and size of the rectangle 601 and the threshold value are unique values depending on the photographing apparatus.

FIG. 7 is a flowchart for determining whether or not the object to be photographed is in contact in the photographing object contact determination apparatus according to the present invention.
First, in step 701, an image of the finger 201 is taken. The width of the image obtained at this time is W, and the height is H.
Step 702 initializes each variable in order to obtain the average luminance inside the rectangle.
In step 703, the luminance integration counter Z is cleared to zero and the y-direction counter iy is cleared to zero.
Step 704 determines whether all lines are listed in the vertical direction of the image.
Step 705 is to clear the x direction counter ix to zero.
Step 706 determines whether all pixels are listed in the horizontal direction of the image.
In step 707, the value of the pixel of interest is added to the integration counter z, and the x-direction counter ix is incremented.
Step 708 increments the y-direction counter iy.
Step 709 obtains the average luminance in the rectangle by dividing the integration result by the number of pixels.
Step 710 compares the obtained average luminance z with a threshold value for determining whether there is a shadow. If the average luminance z is smaller than the threshold value, the finger 201 touches the filter member 205, and z is When it is larger than the threshold value, it is determined that no contact has occurred.

  In the above embodiment, the near-infrared irradiation range is narrower than the shooting range of the camera 204 by blocking near-infrared rays at the L-shaped bottom of the finger rest 208, but FIG. Similar effects can be obtained by arranging the irradiation angle of the near-infrared LED to be tilted toward the base of the finger as shown in other embodiments.

201 Finger 203 to be photographed Near-infrared LED
204 Camera 202 Finger rest 208 Finger rest 205 Filter member 209 Shadow

Claims (1)

A transparent filter member is provided on the lower surface, and it has a finger rest that places from the base part of the finger to be photographed to the tip part, and near infrared light from the palm side to the finger of the object to be photographed placed on this finger rest A near-infrared illumination device that irradiates through the filter member, a camera that captures an image of a finger from the palm side through the filter member, and a finger that processes the finger image captured by the camera, A contact determination unit that determines whether or not it is touching,
The near-infrared illumination device that the near-infrared illumination device irradiates the finger to be imaged with respect to the imaging range of the camera is set to be narrow, and the contact determination unit determines the size of the shadow formed on the tip of the finger. An apparatus for determining contact with an object to be photographed, comprising: determining whether a finger is in contact with a filter surface.

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